Revert "CI: limit the on push triggers (#35574)" (#37657)

This reverts commit f0ae5cceac.

.github/workflows/browserstack.yml

@@ -2,11 +2,6 @@ name: BrowserStack
 
 on:
   push:
-    branches:
-      - main
-  pull_request:
-    branches:
-      - main
   workflow_dispatch:
 
 env:
@@ -19,7 +14,7 @@ permissions:
 jobs:
   browserstack:
     runs-on: ubuntu-latest
-    if: github.repository == 'twbs/bootstrap'
+    if: github.repository == 'twbs/bootstrap' && (!contains(github.event.commits[0].message, '[ci skip]') && !contains(github.event.commits[0].message, '[skip ci]'))
     timeout-minutes: 30
 
     steps: